Functionalization of the SiO2 Surface with Aminosilanes to Enable Area-Selective Atomic Layer Deposition of Al2O3.

Abstract

Small-molecule inhibitors are promising for achieving area-selective atomic layer deposition (ALD) due to their excellent compatibility with industrial processes. In this work, we report on growth inhibition during ALD of Al2O3 on a SiO2 surface functionalized with small-molecule aminosilane inhibitors. The SiO2 surface was prefunctionalized with bis(dimethylamino)dimethylsilane (BDMADMS) and (N,N-dimethylamino)trimethylsilane (DMATMS) through solution and the vapor phase. ALD of Al2O3 using dimethylaluminum isopropoxide (DMAI) and H2O was performed on these functionalized SiO2 surfaces. Our in situ four-wavelength ellipsometry measurements show superior growth inhibition when using BDMADMS and DMATMS in sequence over just using BDMADMS or DMATMS. Vapor phase functionalization provided a growth delay of ∼30 ALD cycles, which was similar to solution-based functionalization. Using in situ attenuated total reflection Fourier transform infrared spectroscopy, we show that the interaction of DMAI with SiO2 surfaces leads to pronounced changes in absorbance for the Si-O-Si phonon mode without any detectable DMAI absorbed on the SiO2 surface. Detailed analysis of the infrared spectra revealed that the decrease in absorbance was likely caused by the coordination of Al in DMAI to O atoms in surface Si-O-Si bonds without the breaking the Si-O-Si bonds. Finally, we postulate that a minimal amount of DMAI remains adsorbed on surface Si-O-Si bonds even after purging, which can initiate ALD of Al2O3 on functionalized SiO2: this highlights the need for higher surface coverage for enhanced steric blocking.